“If you do your oil changes regularly you shouldn’t have a need for an engine flush,” says Dennis Mott, automotive professor at Centennial College in Toronto.
“Ninety-nine per cent of cars on the road will never ever need one.”
In an engine flush, a technician takes out some of the oil and adds a flush additive – a chemical designed to break up carbon deposits inside the engine. The car gets driven so the chemical can work its way through – and then the deposits get loosened and trapped in the filter. Then you get an oil change and a new filter and all the gunk is taken away.
It’s like some of those less pleasant cleanses sold in the health food store – but it’s for your vehicle.
“You have to change the oil after an engine flush, otherwise it would plug up your system,” says Mott. “That’s why they sell them at the same time as oil changes.”
How does gunk build up?
By going too long between oil changes, doing a lot of stop and go driving, or letting your car sit unused for months at a time.
“If your car sits over the winter and oil’s not circulating in the vehicle, condensation builds up,” Mott says. “I have a couple of antique cars that I rarely drive – I’ve gone over to a high performance oil to prevent (build-up) from happening.”
A flush might not be a bad idea if you’re buying a used car with 100,000 km or more on it and don’t know if the oil was changed regularly, Mott says.
Even if your car had some build up, the oil change place probably wouldn’t be able to tell unless they knew of some gaps in your maintenance history. And it’s definitely not something you need regularly.
“No manufacturer in the world is going to recommend one,” Mott says.
“How an oil change place can know if you need one is beyond me.”
Five Benefits of an Engine Flush
Many oil-change chains offer extra services these days, from transmission fluid changes to air conditioning maintenance.
One of the services an oil change technician might suggest next time you're in is an engine flush, which is exactly what it sounds like -- it flushes the gunk out of your engine.
Chemicals are poured into the engine, which is then gently idled for a few minutes to make sure the cleaning agent reaches everyplace oil would normally go. Then the chemicals are drained, just like the oil would be for an oil change. As a matter of fact, an engine flush is often performed after the old oil is taken out and before the new, clean oil is poured in.
Clean is good, but keep in mind that many manufacturers advise against performing and engine flush on modern vehicles. Chris Martin of Honda goes said, "Our engineers have conducted exhaustive tests to create specialized maintenance products and service standards that support the performance and longevity of Honda vehicles, and these standards don't include engine flushing." Engineers at GM said, "Engine oil flushes are not recommended. If oil is changed on schedule, you shouldn't have to flush the engine."
There may be a few instances where an engine flush is required, but be aware that engine technology has progressed to the point that many newer vehicles not only don't need and engine flush, they may be harmed by the procedure.
Keeping that caveat in mind, let's take a look at five benefits of an Engine Flush
1. Clean Engine Parts
If the gunk in the engine oil gets too bad, the parts of the engine can get gummed up. An engine flush removes the gunk, which keeps the parts running smoothly. That in turn can make the engine more efficient, bringing the power and fuel efficiency closer to what the car had when it left the showroom floor.
In very old cars, however, the engine flush might clean these piston rings, valves, and other parts a little too well. Sometimes, the gunk acts as spackle in non-metallic parts like rubber seals that have cracked with age. Cleaning out the gunk exposes those cracks, and the weakness of those parts becomes apparent.
For more information about engine flushing and other related topics, follow the links on the next page.
2. Clean Up What the Filter Misses
Most oil filters remove particles as small as 25 microns (about 1/1000th of an inch) -- but there are particles circulating in your car's oil that are even smaller -- particles that even the newest, best filter can't keep out of the system. And even tiny little bits like that can cause wear over time. They can also band together to create sludge and deposits.
If these particles become excessive, clean oil alone can't flush them out. But the chemicals used in an engine flush can -- stopping any further wear and giving the new oil a chance to do its job properly.
3. Keep New Oil Clean
Especially if you recognize your car's history (or lack of history) on the previous page, an engine flush could help keep your new oil clean. That's why these services are often performed together: First the flush to get rid of old oil deposits, then the new oil to keep the engine in tip-top shape.
Without the engine flush, the new oil will just pick up the old deposits and sludge and keep them circulating through the engine. Soon enough, the new oil is just as dirty as the old oil. An engine flush can help you go longer between oil changes, especially if the maintenance on the car hasn't been perfect.
4. Give Your Car a Clean Slate
While most cars that are driven and maintained regularly don't need an engine flush, there are a few cases where doing an engine flush may help:
Cars with an unknown maintenance record. If you just bought an older used car for a great price but it didn't come with any maintenance records, an engine flush followed by a few quarts of fresh oil might save you a headache later.
Cars with recent internal engine work. You know the maintenance record of this engine -- and it's major. If your car had any engine work done, an engine flush could wash away leftover particulates before adding new oil.
Cars with a long interval between oil changes. Again, you know the service record of this car, and you know the owner rarely (if ever) changed the oil. There's almost certainly buildup in the engine, since dirty oil only gets dirtier. An engine flush could give the car a longer life.
5. Remove Deposit Build-Up
Sometimes, the way we drive keeps engine oil from being able to do its job completely and well. Short trips of only a few miles and lots of stop-and-go driving can cause particles in the oil to become deposits in the engine, which can build up over time. These deposits restrict the flow of oil.
An engine flush can clear out those deposits to open narrow oil passages clogged by gunk that's been floating around in the oil. Releasing those deposits and allowing the oil to flow freely saves wear and tear on the engine and keeps parts moving as they should.
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